Conversion of hydrocarbon oils



June 11, 1940. L.l A. mKLER, 2,203,833:-

1 convERsIoN oF'HYDRocARBoN ons` Filed sept.- so, 1952 2 sheets-sheet 1 `FIG. 2 `INVl-IN'IOR 1 LEv A. MEKLER June l1, 1940. L. vA. MEKLER 2,203,833

CONVERSION OF HYDROGARBON OILS Filed Sept. 30, 1932 2 Sheets-Sheet 2 OOOOOOOO FIG. 3

INVENTOR LEV A. MEKLER `Patented June 11, 1940 CONVERSION OF H'YDROCARBON OILS Lev A. Mekler, Chicago, llll., `assigner to vUniversal i! Products Company, Chicago, ll., a corporation of Delaware Application September 30, 1932, Serial"No. 63`5,49d `14 claims. (en 1196-61),

l `This invention relates to the conversion of `hydrocarbon oils and more specifically refers to i an improved method` and means for heating hydrocarbon oils tothe high temperatures re- `quired fortheir conversion.` y

*i I have found in practice that, much higher rates of heating may be safely employed in the heating sof `hydrocarbon oils while the oil is in a substantiallyliquid state than during the periodin which `the oil is undergoing vaporization or, stated more generally, sensible heat may be safely applied at a more rapid rate than latentheat of Vaporization. When this practice is not followed, as the teml peraturev of the oil increases and evaporation progresses, the remaining liquid becomes progressively heavier and, with highrates of heating and high tube wall temperatures in the fluid conduit, `the `heavy material which drops out land cornes in contact with the hot metal `Walls is crackedito form excessive quantities of coke and gas; leaving a deposit of carbonaceous material 'upon the hot tubes. `It is my belief that this accounts formost of the cokingdiiculties encountered in thecracking of relatively light oils, comprising or containing a high percentage of `naphthas or otherlight` distillates, wherein` substantially complete vaporization or atomization and substantial conversion of the oil is accomplished in the heating coil. However, I have also found thatonce evaporation of the oil has been .substantially completed,. high rates `of heating may again be` safely employed without encountering coking difficulties and my investigationsshow, in fact; that during `the period in whichthe Va- `pers are undergoing substantial conversion an appreciable increase in the amount of heat sup- `plied theretoisrequired` to obtain a temperature riseras the oil passes through this portion of the fluid conduit. Otherwise the `requirements for the latent heat of conversion may be greater than Mthe heat supplied tothe oil andan actual deinvention to provide` an improved method and means of heating and subjecting them to conversion whereby the oil is rst heated at a rapid rate, wherein the initial rate of heating is decreased during' the vaporization period` and,` finally, wherein the rate of heating is again increased duringthe nal heating andv conversion period following substantially complete vaporization or atomization of theoil.

While, as above indicated, the features of the i prsent"inventionl are particularly well adapted tothe `convention orreforming of lightoils such `as naphthas, straight-run gasoline and other light distillates they are not limited to use with any particular type of oil as they may be aclvantageously employed with anyoil when the conversion conditions employed are such that substantially complete vaporization or atomization of the oil `is accomplished in the heating coil.

The phrase substantially complete vaporiza- [tion or atomization of the oil as used herein, is

intended to define a condition of the oil wherein :practically the entire mass of the oil is in a completely vaporized state or exists inthe heating coil` in the form of a mist or fog, so that no detrimental quantity of heavy liquid adheres to the tubewalls where it may be highly heated to form coke.

One specific form of improved. furnace structure and arrangement of the iiuid conduit or heating coil which permits the practice of the features of the present invention is illustrated inthe `attached diagrammatic drawings which consist of Figures 1, 2, 3 and 4.

Figure 1 is a sectional plan view of a furnace;`

"Figure ais a sectional elevation;` Figure 3 is va sectional end View and Figure 4 is a flow diagram` illustrating apreferrred flow of oil through the heating coil of the furnace illustrated in Figures l, 2 and 3. The entire` drawings are diagrammatic and are intended only to illustrate `a practical application of the features of the present invention which` are not limited to this nor to any other particular type of furnace structure.`

ReferringI particularly to Figs. 1,-2 and 3, the furnace structure proper consists of side walls `i and l', front wall 2 and Wall 3, floor 4 and roof 5 enclosing a large combustion zone li.`

The furnace is red with any desired form of fuel by means of burners (not shown) through ducts `'l of firing tunnels 8. Additional ducts 9 are provided in the `firing tunnels for the introduction of auxiliary air or steam.

A fluid heating zone l@ is provided adjacent rear wall 3 Vof the furnace through which hot combustion gases pass to iiue ll and thence to a suitable stack` (not shown). A bank of tubes l2 may be provided in this zone which, in the preferred embodiment ofthe invention, serves only as a preheater section for the recovery of fluid heat from the hot combustion gases leaving the `furnace bythe raw oil` charging stock. The

tubes `I3 of fluid heating bank I2` may be connected in series, as illustrated in the drawings, .by means of` suitable return bends or headers I4 or, when desired, the tubes of the fluid heating cent floor d.

may, of course, be employed, when desired. The

tank may be connected in parallel by well known means, not show in the drawings.

Two rows I and I '6 of radiant tubes I'I are provided adjacent the respective side walls I and I and roof 5 of the furnace. The tubes of row or bank I5 are exposed to direct radiation from the flame in combustion zone 6 and are termed exposed radiant tubes while the tubes of row or bank I6 are partially shielded by the tubes of bank I5 and are therefore termed shielded radiant tubes but are exposed to some direct radial tion from the flame and also to reflected radiation from the side walls and roof of the furnace. The upper portions of side walls Iv and I are preferably recessed, as indicated in the drawings, at points I8 and I8', permitting the side wall tubes in rows I5 and i6 to be set back out of the combustion zone in order to prevent direct impinge-` ment of flame from the firing tunnels upon these tubes. .The tubes of radiant banks I5 and I6 are preferably connected in series, as illustrated in the drawings, by meansof suitable return bends or headers i9.

`A single ro-w 2() of radiant iloor tubes 2i is provided, in therfurnace here illustrated, adja- More than one row of floor tubes floor 4 is preferably depressed ahead of firing tunnels 8,as indicated at 22 in the drawings to prevent flame impingement on the tubes of the radiant floor bank 20. also preferably connected in series by means of `suitable return bends orV headers such as illustrated, for example, at 23.

Referring to Figure 4 which is a flow diagram illustrating a preferred hook-up for the iiow of `oil` through the entire heating coil or fluid conduit of the furnace structure, as illustrated in Figures l, 2 and 3. The heating coil consists, as already described, of preheating or convection bank I2, exposed radiant bank I5', shielded radiant bank Iii and the radiant floor bank 20. As indicated by the direction of the arrows in Figure 4, the oil enters fluid heating or preheating bank I2, iiowing through the tubesr of this bank in series, countercurrent to the ilow of combustion gases, the preheated oil flowing then through the tubes of the exposed radiant bank I5 in series, Where it is heated at a high rate of heat input, then passing through the tubes of shielded radiant bank i6 in series, where it isheated at a lower rate, and, finally, passing in series through the tubes of radiant floor bank 2B where it is again heated at a rapid rate, from which the heated oil leaves the heating lcoil to other portions of the cracking apparatus, not illustrated.

It will be understood that it is not only possible to employ different types of furnace'structures and heating coils than illustrated in the drawings, but it is also possible to employ different flows through the particular'heating coil shown without departing from the scope of the invention, the object of the invention being to heat the oil rst at a rapid rate,vprior to any substantial vaporization thereof, then to heat the oil at a lower rate during the vaporization period and nally to heat the oilagain at a rapid rate, after vaporization or atomization has been substantially completed.

Asan example of another'v possible flow, not 'illustrated in the drawings,A with the same heating coil as that shown, the oil may be rst preheated in fluid heating bank I2, may then pass through Aradiant floor lbank 20,1 then through Tubes 2i of bank 2li are the shielded bank of tubes I6 and finally through the exposed bank of radiant tubes I5.

As a specific example of -conditions typical of the present invention under which an oil may be treated in the various portions of the heatingv coil above illustrated and described, the oil may enter the convection or preheater section at a pressure yof about 800 pounds per square inch and may loe-heated therein at a rate of approximately 5000 B. t..u.s per square foot of circurnferential tube area, leaving the preheater section to enter the exposed radiant wall and roof tubes at a temperature of about '750 F., and being heated in this portion of, the heating coil, at the rate of about A12,000 B. t. u.s per circumferential square foot of tube surface, to a temperature of about 875 F. The oil then passes through the of motor fuel having an anti-knock value as high as an octane number of about 78 and the heating coil may be operated over an almost indefinite period of time without experiencing coking troubles as compared with a period ofoperation of only ten days to two weeks with less favorable heating conditions.

I claim as my invention:

1. In the heating of light hydrocarbon oils of the character of naphtha and gasoline to effect their pyrolytic conversion, the improved method i of heating which comprises rst subjecting the oil while substantially in liquid phase to heating at a rapid rate, then subjecting the oil to heating at a decreased ratev and substantially completely vaporizing it during this heating at the, decreased rate and then again heating it at a relatively rapid rate during the final heating and cracking the oil in vapor phase during such final heating.

2. A method oiheatingiight hydrocarbon oil 3. In ak process for theconversion of light hydrocarbon oil of the character of naphtha and gasoline wherein a continuous stream of oil isr advanced progressively lthrough a heating coil and initially subjected therein to a rapid rate of heating while substantially in liquid phase,. the improvement which comprises reducing the rate of heat input to the oil during vaporization thereof whereby to minimize the deposition of coke in the `heating coil and then cracking the oil in vapor vphase by again heating itunder a relatively high rate of heat input. Y

l. A method 'ofA heating light hydrocarbon oil of the character of naphtha and gasoline to effect its -pyrolytic conversion which comprises passing the oil progressively in a' continuous stream through a heating coil, subjecting it while substantially in liquid phase to a relatively high l thereto and, finally, heating the vaporized oil at l a relatively rapid rate in the latter stages of heatrate of heating in the initial stages of the heati ing coil, wherein the major portion of the heat absorbed by the oil is in the form of sensible heat, reducing the rate of heating in that portion of the heating coil wherein the oil undergoes vaporization and wherein the major and final i portions of the latent heat required for substantially complete vaporization of the oil is imparted knock value, the improvement which comprises supplying the stock to a heating conduit substantially in liquid phase, heating the stock to a high cracking temperature in the heating conduit while flowing therethrough as a stream, discharging the heated stock` from. the heating conduit substantially in vapor phase, and maintaining a lower rate of heat transfer per unit of area of said conduit from a point in advance of that at which substantial vaporization begins to the point at which the phase change substantially ceases than immediately beyond the last mentioned point.

6. In cracking petroleum stocks containing a substantial proportion of gasoline for the production of gasoline fractions of improved anticonduit substantially in vapor phase, and shield` ing said conduit from the source of said radiant energy from apoint in advance of that at which substantial vaporization begins to the point at which the phase change substantially ceases.

'7. In the cracking of light hydrocarbon oils `which are substantially completely Vaporizable under the cracking conditions, the method which comprises heating the oil at arelatively high rate heat input prior of heat input while substantially in liquid phase, then heating the oil at a lower rate of heat input during Vaporization thereof, and, after the oil has been substantially completely Vaporized, cracking it in vapor phase by again heating under a relatively high rate of heat input.

8. In `the cracking of light hydrocarbon oils which are substantiallycompletely vaporizable under the cracking conditions and wherein the oil is Vaporined and then cracked in the vapor phase, the method which comprises4 heating the oilin liquid phase under a relatively high rate of to substantial vaporiaation thereof, then reducing the rate of heating during vaporization of the oil, and, upon completion of the vaporization, again heating the oil under a relatively high rate of heat input to effect the vapor phase cracking thereof.

`substantially in liquid phase, heating the oil to a high cracking temperature in the conduit while `flowing therethrough as a stream, discharging the heated oil from the heating conduit substantially in vapor phase, maintaining a lower rate of heat transfer per unit of area of said conduit from a point in advance of that at which substantial vaporization begins to the point at which the phase change substantially ceases than immediately beyond the last mentioned point, and subjecting the oil in the initial portion of said conduit and while it is substantially in liquid phase to a higher rate of heating than in the portion of the conduit between said points.

`l0. The method as defined in claim' 9 further characterized in that the oil is subjected to vapor phase` cracking `conditions beyond said point at which the phase change substantially ceases.

Y11. In the` cracking of light hydrocarbon oils which are substantially completely vaporizable under the cracking` conditions, the method which comprises supplying the oil to a heating conduit substantially in liquid phase, heating the oil to a high cracking temperaturein the conduit while flowing therethrough as a stream by heat transferred principally as radiant energy, the oil being heated substantially in `liquid phase in a portion of said conduit `directly disposed to the source of radiant energy, discharging the heat'ed oil from the heating conduit substantially in Vapor phase, and shielding said conduit from the source of said radiant energy from a point in advance ofthat at which substantial Vaporization begins tothe point at which the phase change substantially ceases.

12. The method as defined in claim 11 further characterized in that the portion of the' conduit between said points is shielded from the source of radiant energy by the portion of the conduit in which the oil is heated substantially in liquid phase;

13. In the cracking of `light hydrocarbon oils `which are substantially completely vaporizable under the cracking conditions, the method which comprises supplying the oil substantially in liq- `uidphase to a heating conduit exposed to radiant heat, vaporizing the oil substantially completely in one portion of the conduit and vapor phase cracking it in a subsequent portion of the conduit, and shielding from the source of radiant heat the portion of the conduit in which the oil undergoes vaporization and change of phase, said i subsequent portion of the conduit in which the `oil is vapor phase cracked being directly exposed to the source of radiant heat.

14. In the reforming of light hydrocarbon oils containing a substantial proportion of gasoline fractions and which are `substantially completely vaporizable under the reforming conditions, the method which comprises supplying the oil substantially in liquid phase to a heating conduit, vaporizing the oil substantially completely in one portion of the conduit and vapor phase cracking it in a subsequent portion of the conduit, supplying heat to the oil in said subsequent portion of the conduit at a relatively high rate of heat input and maintaining a lower rate of heat input in the portion of the conduit in which the oil undergoes vaporization and change of phase. l l

LEV A. MEKLER. 

